System-on-Chip (SOC) technology operates and controls various types of systems. In general, SOC technology is the assembling of all the necessary electronic circuits and parts for a system (such as a cell phone or digital camera) on a single integrated circuit (IC), generally known as a microchip. SOC devices greatly reduce the size, cost, and power consumption of the system.
During SOC development, debuggers are connected to the debug interfaces (e.g. JTAG port) of the SOCs. To allow synchronous debugging and to save connector pins, all SOCs of the system typically share one debug bus (e.g. CJTAG) and one connector to the debug tool hardware for debugging and testing procedures. Using the debug bus, the system can be debugged (control, status and trace) through a single connector.
Because of the very high degree of integration on a single IC, in many cases, the number of Input/Output (IO) signals off the SOC device are reduced. Furthermore, as chip sizes increase, the number of transistors on a chip increases much faster than the possible number of IO signals off the chip. In many modern chip designs the chip is said to be pad or IO limited, which means that based on the size of the chip, there is insufficient room for all the IO signals that the designers would like, or need, to have routed off the chip. In such environments, in order to lower costs, conserve space, and provide enhanced security, SOCs and Systems in Packages (SiPs) can be configured without debug interfaces making testing and debugging operations problematic. In such cases, analysis is either infeasible or significant effort is needed to solder a debug connector to the board at a time when analysis is needed.